Metallic sintering powder or alloy

ABSTRACT

Metallic sintered alloys, especially sintered steel alloys, are prepared from a composition of metal powder and the alloying components and/or from an alloying powder and admixtures of carbides such as chromium-carbides by pressure and sintering. If desired, a following cold or warm working step may be used to improve the densification. The starting powder composition contains 0.5-50 percent by weight of carbides consisting completely or substantially of complex chromiumcarbides and/or complex manganese-carbides and/or mixed carbides compose these elements.

United States Patent 1 1 Weissmann et al.

[ METALLIC SINTERING POWDER OR ALLOY [75] Inventors: Gerd Weissmann, Munich; Edgar Kuebel, Fuerstenfeldbruck, both of Germany [73] Assignee: Bayer Leichtmetallwerk- Graf Bluecher von Wahlstatt KG, Munich, Germany [22] Filed: Apr. 23, 1973 21 1 Appl. No.: 353,454

[30] Foreign Application Priority Data 2,008,197 7/1971 Germany [451 June 17, 1975 2,000,257 4/1971 Germany OTHER PUBLICATIONS Chemical Abstracts, No. 104306, Vol. 71. 1969, pp. 200 OD l.A5l.

Primary Examiner-Leland A. Sebastian Assistant Examiner-B. Hunt Attorney, Agent, or Firm-Wolfgang G. Fasse; Willard W. Roberts 57 ABSTRACT Metallic sintered alloys, especially sintered steel alloys, are prepared from a composition of metal powder and the alloying components and/or from an alloying powder and admixtures of carbides such as chromium-carbides by pressure and sintering. If desired, a following cold or warm working step may be used to improve the densification. The starting powder composition contains 05-50 percent by weight of carbides consisting completely or substantially of complex chromiumcarbides and/or complex manganesecarbides and/or mixed carbides compose these elements.

18 Claims, No Drawings 1 METALLIC SINTERING POWDER OR ALLOY BACKGROUND OF THE INVENTION This invention relates to metallic sintering alloys, especially sintering steel alloys and powder mixtures for producing such alloys. These powders consist of a composition of metal and the alloying components and/or alloying powder with additions of carbides, for example, chromium carbides. The powder mixtures are pressed and sintered and, if desired, further densificd by a cold or warm processing step.

It is well known to produce alloyed sinter steels of ferrous powder, carbon and alloying components in a metallic condition, for example, powder condition or of alloyed powders which are completed alloys with regard to their chemical composition but in powdered form which is produced, for example, by atomizing of alloyed smelts.

There are also known methods for producing sintered alloyed steels of carbides of the elements of the 4th, 5th and 6th group of the periodical system of the elements or of ferrous-carbonaceous eutectic alloys of said elements together with ferrous or steel powders.

It is also known to use eta-carbides as an alloying component for producing alloyed steels, however, only for producing high speed steels, by way of a powdermetallurgical method. The carbides added according to said conventional method serve as a carburizing or hardness improving agent, whereby up to 10 percent by weight of one or several carbides of vanadium, molybdenum, chromium and titanium are used.

By using conventional sintering methods for producing alloyed steels, it was impossible to produce a sintered steel alloy from alloying components such as chromium and/or manganese, which have a high affinity to oxygen and which cannot be reduced by common sintering processes, whereby the characteristics of the sintered steel alloys should be comparable in their properties to those of metallurgically produced steel alloys comprising chromium and/or manganese, such as construction-steels, tool-steels, valve-steels or the like. Thus, heretofore the characteristics of sintered steel alloys did not match those of metallurgically produced steel alloys. In other words, the mechanical characteristics of well known sinter steel alloys are inferior to steel alloys having an equivalent chemical composition but produced by a smelt-metallurgical process because sintered alloys, as is known, used to always retain a certain porosity impairing the mechanical characteristics. Where alloying components of a high oxygen affinity are used in the well known methods, a further impairment of the mechanical characteristics is caused by oxide inclusions.

OBJECTS OF THE INVENTION In view of the foregoing, it is the aim of the invention to achieve the following objects singly or in combination:

to provide a metallic sintered alloy, which with regard to its chemical composition corresponds to the composition of metallurgically alloyed steels such as construction steels, tool-steels, valve-steels or the like; and

to provide a sintered alloy having mechanical characteristics which are better than those of comparable prior art sintered alloys, especially sintered alloys which are less porous and which are equal in their properties to the characteristics of alloys produced by a smelting metallurgical process.

SUMMARY OF THE INVENTION According to the invention the foregoing objects will be achieved by using for the compressing and sintering process a powder mixture comprising metal and carbide components as well as additives, wherein the carbide components contain 0.5 to 50 percent by weight of the total mixture, and wherein the carbide components consist completely or substantially of complex chromium carbides and/or manganese-carbides and/or mixed carbides of said elements.

By using said carbides in a complex condition according to the invention oxide inclusions are substantially avoided and the porosity of the finished sintered alloy is very much reduced, since the complex carbides have an extremely high resistance to oxidation under the conditions of the sintering process, and because said complex carbides go into solution within the ferrous matrix.

Heretofore, carbides were added mainly as carborizing agents. Contrary thereto, according to the invention, the complex carbides are used as real alloying components generally, for obtaining very good mechanical characteristics and not merely a higher hardness. The great advantage of the method according to the invention is seen in that it enables to use the sintering method for producing steels alloyed with chromium and/or manganese.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS The alloy according to the invention is produced by pressure molding and sintering the mixture or composition, comprising an iron or alloyed steel powder, alloying powder, the complex carbides, and, if desired, further alloying elements. The alloy may then be subjected to an after treatment such as cold or warm deformation, calibrating, hot pressing, die forging, extruding or the like for producing shaped bodies having not only the desired shape but also a very high density.

The complex carbide compositions are of the structure type M C and/or M C and/or M C whereby M is the metal component and C is the carbon. It is also possible to add mixed carbides of the foregoing types.

It is of advantage, if the carbide compositions used according to the invention contain elements of the 4th, 5th, and/or 6th group of the periodical system of elements, whereby these carbides may be used in the form of composed or mixed carbides and whereby the characteristics of the sinter alloy can be influenced in the same manner as is known from the melting metallurgy. Such elements are, for instance, titanium, vanadium, molybdenum, wolfram and noibium.

According to the invention, furthermore, it is possible to use ferrous carbonaceous alloys in addition to the compositions of carbide.

Furthermore, it is possible to add in a manner known as such alloying elements such as boron, aluminum, nitrogen, silicon, sulfur, cerium-mixed metal or the like, to the sintering alloy.

In the following example embodiments of the invention the per cent figures mean per cent by weight of the total composition.

EXAMPLE 1 A mixture of ferrous powder and 2 percent of complex chromium-manganese mixed carbide powder, wherein Cr/Mn are present at the ratio of H125, and to which 0.5 percent of a pressing facilitating agent such as stearic acid was added, was pressed to a blank of a density of 6.5g/cm and sintered for 60 minutes at a temperature of 1200C. The pressed and sintered blank had a density of 6.9g/cm and a Brinell hardness of HB 2.5/1 87.5 of l50kp/mm Thereafter the sintered blank was drop-forged in a die whereby the density was increased to 7.79g/cm and the Brinell hardness to HB 2.5/l87.5 to 250kp/mm EXAMPLE 2 A mixture of an alloyed ferrous powder including 1.6 percent of Ni and 2 percent of complex chromiummanganese mixed carbide powder, wherein Cr/Mn are present at the ratio of l/0.3, 0.05 percent of carbon and 1 percent of a pressing facilitating agent such as stearic acid was pressed to form a blank having a density of 6.0g/cm and sintered at a temperature of 1250C for 30 minutes. The density of the sintered blank was 6.8g/cm and the Brinell hardness l-lB 5/5 was lOkp/mm The sintered blank was repressed under a pressure of 7 tons/cm at a temperature of 1150C whereby a density of 7.76g/cm was achieved. The alloy had a Brinell hardness HB 2.5/187.5 of 340kp/mm a tensile strength of lkp/mm a yield point of 70kp/mm and an impact strength of 5m kp.

EXAMPLE 3 A mixture comprising ferrous powder, 12 percent Nipowder and of complex chromium manganese mixed carbide powder, wherein the ratio of Cr/Mn was l/l and 1 percent of a pressing facilitating agent such as stearic acid was pressed to a blank of a density of 6.3g/cm and sintered at a temperature of 1200C for 60 minutes to reach a density of 7.0g/cm The blank was then densitied by drop-forging in two deforming steps to a density of 7.97g/cm The tensile strength of the alloy was 95kp/mm EXAMPLE 4 A mixture comprising ferrous powder 0.5 percent of Mn, 0.4 percent of Si, percent of complex chromium-carbide containing molybdenum and vanadium in the ratios of Cr/Mo/V 18/1/0. 1 1 percent of a pressing facilitating agent such as stearic acid was pressed to a blank of a density of 6.1g/cm and sintered at a temperature of 1230C for minutes to reach a density of 6.9g/cm The sintered blank was pressed again under a pressure of 6 to 8 tons/cm at a temperature of 1200C to reach a density of 7.66g/cm The alloy was refined to 56 HRC (Rockwell Hardness Cone).

EXAMPLE 5 A mixture of ferrous powder, 7 percent of complex chromium-manganese mixed carbide Cr/Mn Ill, 20 percent of a powdered ferrous manganese alloy 75 percent of Mn, 5 percent of N, and 1.5 percent of a pressing facilitating agent such as stearic acid, was pressed to a blank of a density of 6.2g/cm and sintered at a temperature of 1180C for 60 minutes. The sintered blank was drop-forged and calibrated by a cold process. The final density was 7.75g/cm and the tensile strength of the alloy was 72kp/mm In view of the foregoing it will be noted that the expression complex carbide as used herein refers to carbides of low carbon content, so called carbon poor carbides as distinguished from carbon rich carbides.

Due to the fact that according to the invention complex carbides, that is carbides with a low carbon content, are used, the metals chromium and manganese go into solution in the basic iron mass. This has the advantage of avoiding oxide inclusions to in turn greatly reduce the porosity of the finished sinter alloy. Further, the complex carbides used according to the invention are exceptionally resistant to oxidation in the presence of the sintering conditions.

According to the prior art carbides of high carbon content are added as hardness improving components of hard alloys. Contrary thereto, the addition of low carbon, complex carbides as taught by the invention is for the purpose of achieving especially good mechanical characteristics, especially a high toughness. According to the invention for the first time a sinter steel alloy with chromium and/or manganese has been produced which may be used as structural, sectional steel, the texture of which is free of disturbing porosity.

Although the invention has been described with reference to specific example embodiments, it is to be understood that it is intended to cover all modifications and equivalents within the scope of the appended claims.

What is claimed is:

1. A powder composition for making a sintered steel alloy comprising a mixture of iron powders, and alloying components including carbides in powder form, said carbides being present from 0.5 to 50 percent by weight of the total composition, said carbides comprising an additive and wholly or predominantly carbon deficient carbides selected from the group consisting of chromium carbides, manganese carbides and mixed carbides of chromium and manganese and including the structural types M C, M C M C wherein M is the metal component and C is the carbon component of the carbide.

2. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of iron (Fe) ranging from 0 to 30 percent, cobalt (Co) ranging from 0 to 2 percent, and nickel (Ni) ranging from O to 16 percent, all by weight of the carbides.

3. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of titanium (Ti), zirconium (Zr), and hafnium (Hf) present from 0 to 2 percent, all by weight of the carbides.

4. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of vanadium (Va), niobium (Nb), and tantalum (Ta), whereby the Va is present from 0 to 25 percent, the Nb is present from 0 to 10 percent, and the Ta is present from 0 to 20 percent, all by weight of the carbides.

5. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of chromium (Cr), molybdenum (Mo), and tungsten (W) all present from 0 to 25 percent, all by weight of the carbides.

6. The composition for making a steel alloy according to claim 1, wherein said additive comprises boron ranging from 0 to 25 percent, all by weight of the carbides.

7. The composition for making a steel alloy according to claim 1, further comprising carbon containing ferro-alloys ranging from 0 to 30 percent by weight of the total composition.

8. The composition for making a steel alloy according to claim 1, wherein said wholly or predominantly carbon deficient carbides range from 0.5 to 20 percent by weight of the total composition.

9. A composition for making a sintered steel alloy comprising a mixture of powdered steel alloy or alloys and carbides in powder form, said carbides being present from 0.5 to 50 percent by weight of the totalcomposition, said carbides comprising an additive and wholly or predominantly carbon deficient carbides selected from the group consisting of chromium carbides, manganese carbides, and mixed carbides of chromium and manganese and including the structural types M C, M C M C wherein M is the metal component and C is the carbon component of the carbide.

10. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of iron (Fe) ranging from 0 to 30 percent, cobalt (Co) ranging from 0 to 2 percent, and nickel (Ni) ranging from 0 to 16 percent, all by weight of the carbides.

11. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of titanium (Ti), zirconium (Zr), and hafnium (Hf) present from O to 2 percent, all by weight of the carbides.

12. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of vanadium (Va), niobium (Nb), and tantalum (Ta), whereby the Va is present from 0 to 25 percent, the Nb is present from 0 to percent, and the Ta is present from O to 20 percent, all by weight of the carbides.

13. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of chromium (Cr), molybdenum (Mo), and tungsten (W) all present from 0 to 25 per cent, all by weight of the carbides.

14. The composition for making a steel alloy according to claim 9, wherein said additive comprises boron ranging from 0 to 25 percent, all by weight of the car bides.

15. The composition for making a steel alloy according to claim 9, further comprising carbon containing ferroalloys ranging from O to 30 percent by weight of the total composition.

16. The composition for making a steel alloy according to claim 9, wherein said wholly or predominantly carbon deficient carbides range from 0.5 to 20 percent by weight of the total composition.

17. A powder composition for making a sintered steel alloy comprising a mixture of iron powders, and alloying components including carbides in powder form, said carbides being present from 0.5 to 50 percent by weight of the total composition, said carbides comprising wholly or predominantly carbon deficient carbides selected from the group consisting of chromium carbidc manganese carbides, and mixed carbides of chromium and manganese and including the structural types M C, M C M C wherein M is the metal component and C is the carbon component of the carbide.

18. A composition for making a sintered steel alloy comprising a mixture of powdered steel alloy or alloys and carbides in powder form, said carbides being present from 0.5 to 50 percent by weight of the total composition, said carbides comprising wholly or predominantly carbon deficient carbides selected from the group consisting of chromium carbides, manganese carbides, and mixed carbides of chromium and manganese and including the structural types M C, M C M C wherein M is the metal component and C is the carbon component of the carbide.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N Dated June 17,

lnventofls) Gerd weissmann e1: al

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[30] Foreign Application Priority Data April 27 1972 Germany 2220613 Signed and Sealed this twenty-third Day Of September 1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Alluring ()jficz'r ('vmmisnnm'r 01' Parents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3 890 105 Dated June 17 1975 Inventor) Gerd weissmann e1: a1

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[30] Foreign Application Priority Data April 27 1972 Germany 2220613 Signed and Sealed this twenty-third Day of September 1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN .Mrcsn'ng Officer (ummLYximu'r-uj'lau'nrs and Tradcmarkx 

1. A POWDER COMPOSITION FOR MAKING A SINTERED STEEL ALLOY COMPRISING A MIXTURE OF IRON POWDERS, AND ALLOYING COMPONENTS INCLUDING CARBIDES IN POWDER FROM, SAID CARBIDES BEING PRESENT FROM 0.5 TO 50 PERCENT BY WEIGHT OF THE TOTAL COMPOSITION, SAID CARBIDES COMPRISING AN ADDITIVE AND WHOLLY OR PREDOMINANTLY CARBON DEFICIENT CARBIDES SELECTED FROM THE GROUP CONSISTING OF CHROMIUM CARBIDES, MANGANESE CARBIDES AND MIXED CARBIDES OF CHROMIUM AND MANGANESE AND INCLUDING THE STRUCTURAL TYPES M3C, M7C3, M23C6, WHEREIN M IS THE METAL COMPONENT AND C IS THE CARBON COMPONENT OF THE CARBIDE.
 2. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of iron (Fe) ranging from 0 to 30 percent, cobalt (Co) ranging from 0 to 2 percent, and nickel (Ni) ranging from 0 to 16 percent, all by weight of the carbides.
 3. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of titanium (Ti), zirconium (Zr), and hafnium (Hf) present from 0 to 2 percent, all by weight of the carbides.
 4. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of vanadium (Va), niobium (Nb), and tantalum (Ta), whereby the Va is present from 0 to 25 percent, the Nb is present from 0 to 10 percent, and the Ta is present from 0 to 20 percent, all by weight of the carbides.
 5. The composition for making a steel alloy according to claim 1, wherein said additive is selected from the group consisting of chromium (Cr), molybdenum (Mo), and tungsten (W) all present from 0 to 25 percent, all by weight of the carbides.
 6. The composition for making a steel alloy according to claim 1, wherein said additive comprises boron ranging from 0 to 25 percent, all by weight of the carbides.
 7. The composition for making a steel alloy according to claim 1, further comprising carbon containing ferro-alloys ranging from 0 to 30 percent by weight of the total composition.
 8. The composition for making a steel alloy according to claim 1, wherein said wholly or predominantly carbon deficient carbides range from 0.5 to 20 percent by weight of the total composition.
 9. A composition for making a sintered steel alloy comprising a mixture of powdered steel alloy or alloys and carbides in powder form, said carbides being present from 0.5 to 50 percent by weight of the total composition, said carbides comprising an additive and wholly or predominantly carbon deficient carbides selected from the group consisting of chromium carbides, manganese carbides, and mixed carbides of chromium and manganese and including the structural types M3C, M7C3, M23C6, wherein M is the metal component and C is the carbon component of the carbide.
 10. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of iron (Fe) ranging from 0 to 30 percent, cobalt (CO) ranging from 0 to 2 percent, and nickel (Ni) ranging from 0 to 16 percent, all by weight of the carbides.
 11. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of titanium (Ti), zirconium (Zr), and hafnium (Hf) present from 0 to 2 percent, all by weight of the carbides.
 12. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of vanadium (Va), niobium (Nb), and tantalum (Ta), whereby the Va is present from 0 to 25 percent, the Nb is present from 0 to 10 percent, and the Ta is present from 0 to 20 percent, all by weight of the carbides.
 13. The composition for making a steel alloy according to claim 9, wherein said additive is selected from the group consisting of chromium (Cr), molybdenum (Mo), and tungsten (W) all present from 0 to 25 percent, all by weight of the carbides.
 14. The composition for making a steel alloy according to claim 9, wherein said additive comprises boron ranging from 0 to 25 percent, all by weight of the carbides.
 15. The composition for making a steel alloy according to claim 9, further comprising carbon containing ferro-alloys ranging from 0 to 30 percent by weight of the total composition.
 16. The composition for making a steel alloy according to claim 9, wherein said wholly or predominantly carbon deficient carbides range from 0.5 to 20 percent by weight of the total composition.
 17. A powder composition for making a sintered steel alloy comprising a mixture of iron powders, and alloying components including carbides in powder form, said carbides being present from 0.5 to 50 percent by weight of the total composition, said carbides comprising wholly or predominantly carbon deficient carbides selected from the group consisting of chromium carbides, manganese carbides, and mixed carbides of chromium and manganese and including the structural types M3C, M7C3, M23C6, wherein M is the metal component and C is the carbon component of the carbide.
 18. A composition for making a sintered steel alloy comprising a mixture of powdered steel alloy or alloys and carbides in powder form, said carbides being present from 0.5 to 50 percent by weight of the total composition, said carbides comprising wholly or predominantly carbon deficient carbides selected from the group consisting of chromium carbides, manganese carbides, and mixed carbides of chromium and manganese and including the structural types M3C, M7C3, M23C6, wherein M is the metal component and C is the carbon component of the carbide. 